Gun-control advocates believe their activism will mirror the fight for gay marriage. They’re wrong.

Could last month’s mass shooting in Parkland, Fla., be the tipping point that finally persuades Americans to accept more stringent gun control?

Though mass shootings are depressingly frequent in the United States, the initial shock and horror after each massacre almost invariably segues to frustrated legislative efforts. This time, however, commentators from both sides of the political spectrum sense something different about the moment. And they are pointing to the history of another historic social movement whose success was far from preordained as inspiration: the campaign for gay marriage.

Last year, in a piece titled “Repeal the Second Amendment,” conservative New York Times columnist Bret Stephens wrote, “Repealing the Amendment may seem like political Mission Impossible today, but in the era of same-sex marriage it’s worth recalling that most great causes begin as improbable ones.” The Daily Beast’s Eleanor Clift, a liberal, sees similar parallels, observingthat the 150,000-plus students who have survived a mass shooting and shared their experiences are producing “the same kind of awakening” as gay people whose coming out of the closet led to a “transformation of attitudes toward same-sex marriage.”

The comparison is compelling. Both movements rest upon a broadening of our moral consciousness. Gay activists successfully portrayed the lack of equal marriage as a cruel denial of rights to fellow citizens, while gun-control advocates can point to the thousands of people who die annually in firearms violence as victims of worse injustice. Eventually, the reasoning goes, opposition to stricter gun control will appear like opposition to marriage equality: retrograde and inhumane. Already, New York Times columnist David Brooks has observed that “certain ideas about gun rights, and maybe gun ownership itself, are being cast in the realm of the morally illegitimate and socially unacceptable,” just like opposition to same-sex marriage.

But there is a critical flaw in this comparison: While gun-control activists indeed appear to be pursuing a strategy similar to that adopted by marriage equality campaigners — culminating in Saturday’s March for Our Lives on the Mall, where speakers attempted to morally shame their adversaries — marriage equality didn’t require straight people to surrender anything. Eventually, it became clear to most heterosexual Americans that allowing gay people to marry would have no detrimental effect on their own marriages or the institution of marriage itself. ...